CustomTags has a virtual destructor

[mvanslobbe]

When compiling with '-Wnon-virtual-dtor' the current code will lead to

Common.h:214:7: warning: 'quill::CustomTags' has virtual functions but non-virtual destructor [-Wnon-virtual-dtor]
class CustomTags

This fixes that.

[odygrd]

Hey, thanks for the PR.
How are you using custom_tags ?

It has to be used as in this example
https://github.com/odygrd/quill/blob/master/examples/example_custom_tags.cpp#L39

If you add the virtual destructor then it doesn't compile anymore.

e.g.

example_custom_tags.cpp:39:32: error: the type ‘const MyCustomTagsA’ of ‘constexpr’ variable ‘custom_tags_a’ is not literal
   39 | static constexpr MyCustomTagsA custom_tags_a{"CUSTOM_TAG_A", 12};

It seems that instead of adding a virtual dtor, we need to ignore this warning for this class

[odygrd]

moving this to #405